This invention relates to a filter unit for reverse filtration of a liquid sample, especially a biological fluid.
In many tests for the determination of specific components in a biological fluid, a filtered sample of the fluid must be used to avoid any interference in the test by solid matter. Usually, the fluid is poured into a filtering unit wherein the filtered fluid, with the aid of gravity, drops to a container below. The pouring of the unfiltered fluid into the filtering unit can often be unpleasant for some people because of its odors and appearance. Furthermore, unskilled operators will frequently spill the biological fluid.
The filtering unit of this invention provides a sample of a filtered liquid in a simple one step operation and overcomes many of the above noted disadvantages. The unit permits the operation to be performed quickly and efficiently with minimal operation instructions. The unit can be produced readily from inexpensive materials so that it can be disposed after use.
A rather extensive number of various filtering devices are described and known. Representative filtering devices are described in the following reports: P. N. Rigopulos, U.S. Pat. No. 3,483,768, Jan. 6, 1970; J. Dillon, U.S. Pat. No. 169,092, Oct. 26, 1875; H. More, U.S. Pat. No. 185,866, Jan. 2, 1877; H. More, U.S. Pat. No. 203,847, May 21, 1878; J. W. Pheils, U.S. Pat. No. 1,115,016, Oct. 27, 1914; P. J. Bacher, U.S. Pat. No. 1,193,970, Aug. 8, 1916; J. A. Roosevelt et. al., U.S. Pat. No. 1,471,807, Oct. 23, 1923; E. F. Pierce, U.S. Pat. No. 1,671,606, May 29, 1928; E. F. White, U.S. Pat. No. 1,780,774, Nov. 4, 1930; G. F. Thomas et al., U.S. Pat. No. 1,781,964, Nov. 18, 1930; C. V. Lundeen, U.S. Pat. No. 2,641,365, June 9, 1953; C. Oakley, U.S. Pat. No. 3,266,411, Aug. 16, 1966 and A. D. Nash, U.S. Pat. No. 1,937,203, Nov. 28, 1933. The above described filtering devices differ in form and function when compared to the filtering unit of this invention.